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BSI PD IEC TS 62738:2018

$189.07

Ground-mounted photovoltaic power plants. Design guidelines and recommendations

Published By Publication Date Number of Pages
BSI 2018 50
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This document sets out general guidelines and recommendations for the design and installation of ground-mounted photovoltaic (PV) power plants. A PV power plant is defined within this document as a grid-connected, ground-mounted system comprising multiple PV arrays and interconnected directly to a utility’s medium voltage or high voltage grid. Additional criteria is that PV power plants are restricted from access by non-qualified persons and are continuously monitored for safety and protection, either by on-site personnel or by active remote monitoring. Technical areas addressed are those that largely distinguish PV power plants from smaller, more conventional installations, including ground mounted array configurations, cable routing methods, cable selection, overcurrent protection strategies, equipotential bonding over large geographical areas, and equipment considerations.

Safety and design requirements are referenced to the applicable requirements of IEC 62548 to address distinct differences relative to the design requirements for residential, commercial and other non-power plant applications. In general, existing standards are referenced wherever possible for uniformity. Emphasis is placed on systems employing d.c. string based systems using large scale central inverters or 3-phase string inverters, but relevant sections are also applicable to systems employing a.c. modules or d.c./d.c. converters. Medium voltage transformers, switchgear, collection systems, substations, utility interconnection, auxiliary loads, energy storage systems, and communication services are addressed, but discussion is mostly limited to recommended references to other standards and requirements.

Rooftop-mounted systems, building integrated PV (BIPV) and building applied PV (BAPV) are not included in the scope of this document. The principles of restricted-access power plants are not compatible with systems on buildings, which are used for purposes other than power generation.

PDF Catalog

PDF Pages PDF Title
2 undefined
4 CONTENTS
7 FOREWORD
9 INTRODUCTION
10 1 Scope
2 Normative references
13 3 Terms and definitions
4 Compliance with IEC 62548
14 5 PV array system configuration
5.1 General
5.2 Earthing configurations
5.2.1 General
5.2.2 Use of un-earthed d.c. circuits
5.2.3 Use of high-ohmic earthed d.c. circuits
5.2.4 Use of functionally earthed d.c. circuits
5.3 Array electrical diagrams
5.3.1 General
15 5.3.2 Multiple sub-array configurations
Figures
Figure 1 – PV array diagram – multiple parallel string case with array divided into sub-arrays
16 Figure 2 – PV array example using a PCE with multiple MPPT d.c. inputs
17 5.3.3 Single array configuration
Figure 3 – PV array using a PCE with multiple d.c. inputs internallyconnected to a common d.c. bus
18 5.3.4 Combiner boxes and string wiring harnesses
5.3.5 Series-parallel configuration
Figure 4 – PV array diagram – multiple parallel string example
19 5.4 Energy storage in PV power plants
5.5 Array physical configurations
5.5.1 Fixed tilt arrays
5.5.2 Adjustable tilt arrays
Figure 5 – Example power plant with fixed tilt array
20 5.5.3 Single axis tracking arrays
5.5.4 Two-axis tracking arrays
5.5.5 Concentrating PV arrays
5.5.6 Central inverter configurations
21 5.5.7 String or module inverter configurations
Figure 6 – Example layout of power plant central inverter based array
22 5.6 Mechanical design
5.6.1 Mechanical loads on PV structures
5.6.2 Wind
5.6.3 Snow
5.6.4 Thermal expansion
5.6.5 Flooding
Figure 7 – Example layout of power plant with string inverters
23 5.6.6 Seismic activity
5.6.7 Corrosion
5.6.8 Access
6 Safety issues
6.1 General
24 6.2 Restricted access
6.2.1 General
6.2.2 Access to components
6.3 Protection against overcurrent
6.3.1 DC overcurrent protection devices
6.3.2 Requirement for string overcurrent protection
6.3.3 String overcurrent protection sizing
25 6.3.4 PV sub-array and array overcurrent protection
26 6.4 Protection against the effects of insulation faults
6.5 Protection against effects of lightning and overvoltage
6.5.1 Lightning protection
27 Figure 8 – Example ground plan for equipotential bondingof a PV array field
28 6.5.2 Protection against overvoltage
6.6 Protection against fire
6.6.1 Earth-fault protection
6.6.2 Protection against arcing currents
7 Selection and erection of electrical equipment
7.1 General
29 7.2 PV array design voltage
7.2.1 PV array maximum voltage
7.2.2 Considerations due to inverter MPPT voltage window
7.2.3 Considerations due to inverter efficiency
7.3 Component requirements
7.3.1 General
30 7.3.2 PV combiner boxes
31 7.3.3 Disconnectors and switch-disconnectors
32 7.3.4 Cables
34 Figure 9 – Example of above-ground cable tray configurations for PV plants
36 Figure 10 – Example trench diagram with cables in ducts
37 Figure 11 – Example trench diagram with direct buried d.c.and communication cables
38 Figure 12 – Example trench diagram with direct buried medium voltage a.c.and communication cables
39 7.3.5 Trackers
8 Acceptance
8.1 General
8.2 Monitoring
8.3 Commissioning tests
8.4 Preliminary performance acceptance test
8.5 Final performance acceptance test
40 9 Maintenance
10 Marking and documentation
10.1 General
10.2 Labelling and identification
10.2.1 General
10.2.2 Labelling of disconnection devices and combiner boxes
10.3 Documentation
41 11 Medium and high voltage a.c. systems
11.1 General
11.2 Selection of a.c. collection system voltage
11.3 Collection system configurations
11.3.1 General
11.3.2 Radial systems
42 11.3.3 Loop systems
11.4 Medium or high voltage transformers
11.4.1 Transformer types
11.4.2 Installation
43 11.4.3 Protection
11.5 Medium or high voltage switchgear and stations
11.5.1 General
11.5.2 Switchgear specifications
11.6 Medium voltage cable
44 11.7 Utility interface
12 Auxiliary power systems
13 Communications systems
13.1 General
13.2 Data sampling speed requirements
45 Annex A (informative)Inverter application considerations in PV power plants
A.1 General
A.2 Advantages and disadvantages of central inverters
A.3 Advantages and disadvantages of string inverters
46 A.4 Issues affecting inverter size
A.4.1 PV array output
A.4.2 Inverter ratings
A.4.3 Inverter output control requirements
A.4.4 PV power to inverter power ratio (PVIR)
48 Bibliography
BSI PD IEC TS 62738:2018
$189.07